The present invention relates generally to molding compositions and, more particularly, to a thermoplastic elastomeric molding composition the primary polymeric constituent of which comprises a vulcanizable, or otherwise thermosetable elastomer of the ethylene propylene type sometimes referred to herein as an EPR elastomer.
The molding compositions disclosed herein are suitable for use in the fabrication of a wide variety of elastomeric products such as, for example, semi-pneumatic tires, belting, automotive bumper guards, door stops, rubber covered handles, snap-on-tread tires, hosing, electrical connector jackets and sheet material, all of which may be fabricated employing conventional thermoplastic forming techniques including, for example, injection molding, blow molding, compression molding, transfer molding and conventional extrusion techniques.
In recent years the use of thermoplastic elastomeric molding compositions has become increasingly widespread since such compositions may be molded to form useful elastomeric articles without requiring vulcanization as is the case with thermoset molding compositions. Articles molded from such thermoplastic elastomeric molding compositions frequently possess physical properties as good as if not superior to vulcanized elastomeric articles, and therefore the reduction in production time and expense resulting from elimination of the vulcanization step achieves a significant advantage.
Another advantage thermoplastic elastomeric molding compositions have over thermoset molding compositions is that they may be reprocessed without the necessity of first having to devulcanize them as is normally required when reprocessing articles molded from thermoset compositions.
Certain physical properties of thermoplastic elastomeric molding compositions are of particular importance when determining the desirability of a particular molding composition. The primary elastomeric polymeric cconstituent of the composition should have a high green strength and the resultant composition should have moderate viscosity and high nerve. Additionally, the cost of the particular composition should be competitive with comparable thermoset compositions. Above all, the physical properties of articles molded from thermoplastic molding compositions should compare favorably to the physical properties of comparable thermoset articles.
Against the foregoing background, it is a primary objective of the present invention to provide a thermoplastic elastomeric molding composition processable into a useful elastomeric article.
It is another object of the present invention to provide a thermoplastic elastomeric molding composition, the primary elastomeric polymeric ingredient of which is a sulfurcurable thermosetable compound.
It is another object of the present invention to provide a thermoplastic elastomeric molding composition having moderate viscosity, high nerve and which includes a polymeric ingredient having high green strength.
It is an additional object of the present invention to provide a thermoplastic elastomeric molding composition processable into a useful article, the physical properties of which equal or exceed those of articles produced from thermosetable elastomeric molding compositions which have undergone vulcanization.
It is still another object of the present invention to provide a thermoplastic elastomeric molding composition processable into a useful article which is less expensive than similar articles molded from a thermosetable elastomeric molding composition which has undergone vulcanization.
It is yet still another object of the present invention to provide a novel process for forming a useful elastomeric article.